Systems and Methods of EUV Mask Cleaning

ABSTRACT

A system includes a bracket that is configured to support a photomask and is located at a first side of the photomask; an acoustic energy generator configured to generate acoustic energy, wherein the acoustic energy includes mechanical vibrations of a megasonic frequency and wavelength; and a fluid dispenser coupled to the acoustic energy generator such that the acoustic energy generated by the acoustic energy generator is received by the fluid dispenser to generate an acoustically agitated fluid stream directed at a second side of the photomask, wherein the first side of the photomask is opposite a second side of the photomask, and wherein the first side includes a pattern.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofIC processing and manufacturing. For these advances to be realized,similar developments in IC processing and manufacturing are needed. Forexample, the need to perform higher resolution lithography processesgrows.

One lithography technique is extreme ultraviolet lithography (EUVL). TheEUVL employs a photomask to be exposed in the extreme ultraviolet (EUV)region so as to form a pattern on a substrate. Generally, a photomaskemployed in the EUVL is referred to as a EUV photomask. Light in the EUVregion has a wavelength in the range from about 1 nm to about 100 nm.

While existing lithography techniques have been generally adequate fortheir intended purposes, they have not been entirely satisfactory inevery aspect. For example, the reuse of EUV photomasks in EUVL processeshas given rise to issues.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a system to clean a photomask in accordance withembodiments of the present disclosure.

FIG. 2 illustrates an example of an extreme ultra violet (EUV) photomaskin accordance with some embodiments of the present disclosure.

FIG. 3 illustrates a method of using the system of FIG. 1 to clean aphotomask in accordance with some embodiments of the present disclosure.

FIGS. 4A-4B illustrate examples of sensed acoustic pressure on multiplepoints of the photomask in response to an acoustic energy generator inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIG. 1 is a simplified view of a system 100 that used to clean aphotomask 102, constructed in accordance with some embodiments. In aspecific embodiment discussed below, the photomask 102 is an extremeultraviolet (EUV) photomask. Details of the structure of an EUVphotomask will be provided in the example 200 with respect to FIG. 2.However, the system 100 may be used to clean other items such assubstrates and/or wafers, and still fall within the scope of the presentdisclosure.

Referring to FIG. 1, the system 100 includes a bracket 122 that isconfigured to support and rotate the photomask 102. The bracket 122further includes a support finger 104, and a support post 106. In theillustrated embodiments, although the support finger 104 is shown tosupport the photomask 102 (i.e., in contact with only back side of thephotomask 102-B), in some alternative embodiments, the finger 104 mayserve as a clamp of the photomask 102. The front side 102-F of thephotomask 102 includes a pattern of features. Such a pattern of featuresmay be associated with a semiconductor device or portion thereof, suchas a plurality of gate structures (e.g., polysilicon features, metalgate features, etc), source/drain regions, interconnect lines or vias,dummy features, and/or other suitable patterns. The back side 102-B ofthe photomask 102 does not include a pattern of feature. As shown, backside 102-B of the photomask 102 is opposite the front side 102-F of thephotomask 102.

Referring still to FIG. 1, the system 100 includes a nozzle 118 directed(or adjacent) at the front side 102-F of the photomask 102, a nozzle 108directed (or adjacent) at the back side 102-B of the photomask 102, andan acoustic energy generator 110 coupled to the nozzle 108 at the backside 102-B of the photomask 102. In some embodiments, a spray 119 (e.g.,a chemical solution) is dispensed from the nozzle 118 and is incidentthe front side 102-F of the photomask 102. Similarly, a fluid stream (orfluid path) 120 is dispensed from the nozzle 108 incident the back side102-B of the photomask 102.

In some specific embodiments discussed below, the fluid stream 120dispensed from nozzle 108 is incident the back side of the photomask 102with an angle, “θ”. Details of the operation of the acoustic energygenerator 110 and the back side nozzle 108 will be provided below andthe flow chart with respect to FIG. 3.

Extreme ultraviolet lithography (EUVL) is a promising patterningtechnology for very small semiconductor technology nodes, such as 14 nm,and beyond. EUVL is very similar to optical lithography in that it needsa photomask to print wafers, except that it employs light in the EUVregion that ranges from about 1 nm to about 100 nm. Most commonly, lightused in the EUVL process is about 13.5 nm.

FIG. 2 shows an embodiment of an EUV photomask 200 used in EUVL inaccordance with various embodiments. In general, a variety of photomasksmay be used in the EUVL, and the disclosed method to clean suchphotomasks still falls within the scope of the present disclosure. Forexample, the EUV photomasks may include binary intensity photomasks(BIM) and phase-shifting photomasks (PSM). An example of BIM includes analmost totally absorptive region (also referred to as a dark region) anda reflective region. In the opaque region, an absorber is present andincident light is almost fully absorbed by the absorber. In thereflective region, the absorber is removed and incident light isreflected by a multilayer (ML). A PSM includes an absorptive region anda reflective region. The phase difference (generally 180°) between aportion of a light reflected from the absorptive region and a portion ofthe light reflected from the reflective region enhances resolution andimage quality. The PSM can be an attenuated PSM (AttPSM) or analternating PSM (AltPSM). An AttPSM usually has a reflectivity of 2%-15%from its absorber, while an AltPSM usually has a reflectivity of largerthan 50% from its absorber.

Referring still to FIG. 2, the photomask 200 includes a mask substrate202 made of low thermal expansion material (LTEM). The LTEM material mayinclude TiO₂ doped SiO₂, and/or other low thermal expansion materials.The LTEM substrate 202 serves to minimize image distortion due to maskheating. In an embodiment, the LTEM substrate includes materials with alow defect level and a smooth surface. In addition, a conductive layer204 may be formed on the backside surface of the LTEM substrate 202 (asshown in FIG. 2) for the electrostatic chucking purpose. In anembodiment, the conductive layer 204 includes chromium nitride (CrN), orother suitable conductive material.

The photomask 200 includes a reflective multilayer (ML) 206 disposedover the mask substrate 202 on the front surface (i.e. opposite thesurface on which the conductive layer 204 is formed). In accordance withthe Fresnel equations, light reflection occurs when light propagatesacross an interface between two materials of different refractiveindices. The greater the difference between the refractive indices oflayers, the higher the intensity of the reflected light becomes as itpropagates across the layers. To increase the intensity of the reflectedlight, in some embodiments, a multilayer of alternating materials may beused to increase the number of interfaces so as to cause the lightreflected from each of the different interfaces to interfereconstructively. The ML 206 includes a plurality of film pairs, such asmolybdenum-silicon (Mo/Si) film pairs (e.g., a layer of molybdenum aboveor below a layer of silicon in each film pair). Alternatively, the ML206 may include molybdenum-beryllium (Mo/Be) film pairs, or any suitablematerial that is highly reflective at EUV wavelengths. The thickness ofeach layer of the ML 206 depends on the EUV wavelength and the incidentangle. The thickness of the ML 206 is adjusted to achieve a maximumconstructive interference of the EUV light reflected at each interfaceand a minimum absorption of the EUV light by the ML 206. The ML 206 maybe selected such that it provides a high reflectivity to a selectedradiation type and/or wavelength. In a specific example, the number ofthe film pairs in the ML 206 may range from 20 to 80, however any numberof film pairs may be used. In one example, the ML 206 includes fortypairs of layers of Mo/Si. In such an example, each Mo/Si film pair has athickness of about 7 nm and ML 206 has a total thickness of 280 nm. Inthis case, a reflectivity of about 70% is achieved.

The photomask 200 includes a protection layer 208 formed over the ML 206for one or more functions. In one example, the protection layer 208functions as an etch stop layer in a patterning process or otheroperations, such as repairing or cleaning. In another example, theprotection layer functions to prevent oxidation of the ML 206. Theprotection layer 208 may include a single film or multiple films toachieve the intended functions. In some embodiments, the protectionlayer 208 includes a buffer layer disposed over the ML 206 and a cappinglayer disposed over the buffer layer. The buffer layer is designed toprevent oxidation of the ML 206. In some examples, the buffer layer mayinclude silicon with about 4-7 nm thickness. In other examples, a lowtemperature deposition process may be chosen to form the buffer layer toprevent inter-diffusion of the ML 206. With regard to the capping layerformed over the buffer layer, such capping layer may be formed over thebuffer layer to act as an etching stop layer in a patterning orrepairing/cleaning process of an absorption layer. The capping layer hasdifferent etching characteristics from the absorption layer. Inaccordance with various illustrative embodiments, the capping layerincludes ruthenium (Ru), Ru compounds such as RuB, RuSi, chromium (Cr),Cr oxide, and Cr nitride. A low temperature deposition process is oftenchosen for the capping layer to prevent inter-diffusion of the ML 206.

The photomask 200 also includes an absorption layer 210 is formed overthe protection layer 208. In an embodiment, the absorption layer 210absorbs radiation in the EUV wavelength range projected onto a patternedmask. The absorption layer 210 includes multiple film layers with eachfilm containing chromium, chromium oxide, chromium nitride, titanium,titanium oxide, titanium nitride, tantalum, tantalum oxide, tantalumnitride, tantalum oxynitride, tantalum boron nitride, tantalum boronoxide, tantalum boron oxynitride, aluminum, aluminum-copper, aluminumoxide, silver, silver oxide, palladium, ruthenium, molybdenum, othersuitable materials, and/or mixture of some of the above.

Still referring to FIG. 2, in some embodiments, the absorption layer 210may be patterned according to an IC layout pattern (or simply ICpattern). For example, as shown in FIG. 2, the absorption layer 210 ispatterned to define opaque regions 230 and reflective regions 240. Inthe opaque region 230, the absorption layer 210 remains on the photomask200 while in the reflective region 240, the absorption layer 210 isremoved.

Although the environment in which the EUVL process is performed is keptrelatively clean, there are still contaminants formed on the front/backsides of the photomask. For example, some contaminant organics (e.g.,residual photoresist stripes) may be formed on the front side of thephotomask. Such contaminant organics are generally distributed in sizeof about 50 to 100 nanometers, and frequently distributed within apattern. On the other hand, some relatively large contaminant particlesmay be formed over the back side of a photomask. The size of thecontaminant particles on the back side of a photomask may be about 3 to50 micrometers. Regardless of which kind of contaminants formed on aphotomask, those contaminants may otherwise interfere with thepatterning process if they get on the photomask. For example, thepresence of contaminant particles may lead to defocus or out-of-focusissues. Therefore, a cleaning process may be needed to dislodge suchcontaminants after each lithography process. Conventionally, due to thedifferent sizes of the contaminants formed on each side of a photomask,at least two or more cleaning processes may be needed to dislodge thecontaminants formed on both sides of the photomask. In an example, aspray with a first intensity may be used to clean the contaminantorganics on the front side of the photomask, subsequently a spray with asecond intensity may be used to clean the contaminant particles on theback side of the photomask. As mentioned above, since the differentsizes of the contaminants on each side of the photomask, the firstintensity and second intensity may be different. Moreover, sinceconventional cleaning systems may only include one nozzle, a nozzleconfigured to disperse different intensities of spray and a flippingprocess may be needed. Such flipping process may cause not onlyadditional contaminants formed on the front side of the photomask duringthe cleaning of the back side of the photomask, but also result in extratime consumption to clean the photomask.

Thus, the present disclosure provides systems and methods to provide anin-situ cleaning process on both sides of a photomask. That is, eventhough there may be different sizes of contaminants formed on each sideof a photomask, the disclosed embodiment dislodges the contaminantsformed on both sides of a photomask simultaneously.

Referring now to FIG. 3, a flow chart is shown to illustrate a method300 of cleaning a photomask in accordance with various embodiments. Themethod 300 is described in conjunction with the system 100 of FIG. 1 andthe photomask 102 of FIG. 1 and/or the photomask 200 of FIG. 2. Althoughin the illustrative embodiment of FIG. 3, the method 300 is directed tocleaning a EUV photomask, the presently disclosed method 300 may beapplied to clean a variety of types of photomasks and/or wafers.

The method 300 starts in block 302 with supporting and rotating thephotomask 102/200. As described above, the bracket 122 may be used tosupport and rotate the photomask 102/200. In some embodiments, arotation speed of the photomask 102/200 may range from 0 radius perminute (rpm) to 500 rpm. That is, the photomask 102/200 may bestationary (i.e., 0 rpm) or may move horizontally in a spinning motionduring following blocks 304-308.

The method 300 continues in block 304 in which the fluid stream 120 isapplied, though the nozzle 108, onto the back side of the photomask(e.g., 102-B). The fluid stream is composed of cleaning fluid (a firstchemical solution) that includes at least one of: ozone water,teramethylammonium hydroxide (TMAH), carbon dioxide (CO₂) dissolved inwater, hydrogen (H₂) dissolved in water, and standard clean 1 (SC1).More specifically, the incident angle “θ”, as described above in FIG. 1,may range from about 60 degrees to about 90 degrees.

Subsequently, the method 300 continues in block 306 where the acousticenergy generator 110 generates a mechanical vibration to the photomask102/200 through the fluid stream 120. That is, the acoustic energygenerator 110, coupled to the nozzle 108, is configured to generate anacoustic wave, then propagate the generated acoustic wave through thefluid stream 120 to form an acoustically agitated fluid stream whichcauses the fluid stream 120 applied to the back side of the photomask102/200 to generate a mechanical vibration to the photomask 102/200 viathe acoustically agitated fluid stream. Such an acoustically agitatedfluid stream forms microbubble(s) mechanically vibrating in a frequencywithin the fluid stream 120 and the vibrating microbubbles may be usedto dislodge the contaminants formed on the back side of the photomask102/200. Generally, such a microbubble may be sized in a diameter ofabout 3 micrometers.

Still referring to block 306 of the method 300, in accordance withvarious embodiments, the frequency of the mechanical vibration generatedby the acoustic energy generator 110 may range from about 1 megahertz toabout 3 megahertz. Such frequency is generally referred to megasonicfrequency. Alternatively or additionally, a variety of frequencies maybe used in the disclosed system 100 to clean a photomask, for example,an ultrasonic wave (i.e., frequency between about 20 kilohertz to about400 kilohertz) may be generated by the acoustic energy generator 110.

The method 300 continues in block 308 in which the nozzle 118 dispersesthe spray 119 onto the front side of the photomask 200. In someembodiments, the spray 119 may include a second chemical solution thatis different than the first chemical solution discussed above. In otherembodiments, the first and second chemical solutions are the same. Thesecond chemical solution may include sulfide acid, hydrogen peroxide, ora combination (i.e., SPM) thereof. In some other embodiments, equipmentto generate plasma, aqueous ozone (DIO₃), and/or acoustic wave (e.g.,megasonic wave) may also be combined with the nozzle 118 to remove thecontaminants (e.g., photoresist strips) formed on the front side of thephotomask 102/200. In an example of using the acoustic wave, an acousticenergy generator (different from or the same as the acoustic energygenerator 110) may be thus coupled to the nozzle 118 so as to produce anacoustically agitated fluid stream.

It is understood that additional blocks/processes may be performedbefore, during, and/or after the blocks 302-308, and/or some describedblocks may be combined. For example, blocks 304-308 may be combined as asingle step. That is, during the cleaning process of the photomask102/200, the fluid stream 120 vibrating in megasonic frequency and thespray 119 is respectively applied to the back side and the front side ofthe photomask 102/200 at the same time. It is also noted that thephotomask is not flipped during blocks 302-308 in some embodiments. Thelack of photomask flipping prevents and limits previously removedcontaminants from reattaching the photomask during the cleaning process.

FIGS. 4A and 4B show an example of acoustic pressure sensed in multiplepoints on a photomask in accordance with various embodiments. Asdescribed above, as an acoustically agitated fluid stream is applied ona surface of a photomask, microbubbles are induced in the stream offluid so as to dislodge contaminants on the applied surface. Generally,the intensity and/or the effect of the acoustically agitated fluidstream on the surface may be quantified by acoustic pressure sensed onthe surface. In FIG. 4A, a nozzle 404 (may be considered ascorresponding to nozzles 108 and/or 118 discussed above) generates anacoustically agitated fluid stream 406 on a back side of a photomask 402(may be considered as corresponding to photomasks 102/200 discussedabove). While the acoustically agitated fluid stream 406 is applied ontothe photomask 402, sensors 401, 403, 405, and 407 are deployed atdifferent points on the photomask 402 to monitor the acoustic pressure.In the illustrated embodiment of FIG. 4A, sensor 401 is placed at theback side of the photomask and at the point of the photomask to whichthe acoustically agitated fluid stream 406 is incident; sensor 403 isalso placed at the same point of the photomask to which the acousticallyagitated fluid stream 406 is incident but placed at the front side ofthe photomask; sensors 405 and 407 are both placed at the front side ofthe photomask and respectively displaced from the point of the photomaskto which the acoustically agitated fluid stream 406 is incident with ahorizontal distance. FIG. 4B shows an example of sensed acousticpressure monitored by each of the sensors 401, 403, 405, and 407. Line420 corresponds to a relationship between the pressure monitored by thesensor 401 and the acoustic power provided by the acoustic energygenerator 110. Line 430 corresponds to a relationship between thepressure monitored by the sensor 403 and the acoustic power provided bythe acoustic energy generator 110. Line 440 corresponds to arelationship between the pressure monitored by the sensor 405 and theacoustic power provided by the acoustic energy generator 110. Line 450corresponds to a relationship between the pressure monitored by thesensor 407 and the acoustic power provided by the acoustic energygenerator 110.

As illustrated in FIG. 4B, line 420 shows a relatively higher amount ofacoustic pressure than lines 430-450, which means that although thevibration of the photomask 402 is induced by the acoustically agitatedfluid stream that is incident from the back side of the photomask 402,the photomask as a whole still vibrates in a similar fashion. Moreover,as dotted line 421 in FIG. 4B indicates, the acoustic power monitored bythe sensor 401 saturates at the right side of the dotted line 421. Thisimplies that once the megasonic power provided by the acoustic energygenerator exceeds a threshold (e.g., 421), the acoustic pressure may notincrease accordingly.

Based on the above discussions, it can be seen that the presentdisclosure offers various advantages. It is understood, however, thatnot all advantages are necessarily discussed herein, and otherembodiments may offer different advantages, and that no particularadvantage is required for all embodiments.

One of the advantages is that the present disclosure offers a novel wayof cleaning a photomask. As discussed above, by using the presentlydisclosed method and system, the front side and the back side of thephotomask may be cleaned at the same time while using two differentapproaches to each of the sides of the photomask. In some embodiments,since, in general, contaminants formed on the back side of the photomaskmay have relatively larger size than those formed on the front side,using the disclosed method and system may perform an “in-situ” cleaningprocess. Moreover, since each of the front side and the back side iscleaned individually, no flipping process is needed, which mayadvantageously avoid any cross-contaminants being formed during such aflipping process.

The present disclosure provides a system for cleaning a photomask inaccordance with some embodiments. The system includes a bracket that isconfigured to support the photomask and is located at a first side ofthe photomask; an acoustic energy generator configured to generateacoustic energy, wherein the acoustic energy includes mechanicalvibrations of a megasonic frequency and wavelength; and a fluiddispenser coupled to the acoustic energy generator such that theacoustic energy generated by the acoustic energy generator is receivedby the fluid dispenser to generate an acoustically agitated fluid streamdirected at a second side of the photomask, wherein the first side ofthe photomask is opposite a second side of the photomask, and whereinthe first side includes a pattern.

The present disclosure provides a system of cleaning a substrate inaccordance with some embodiments. The system includes a bracket that isconfigured to support and horizontally rotate a substrate having a topsurface and an opposing bottom surface, wherein the top surface includesa pattern; a first nozzle, located adjacent the bottom surface of thesubstrate, configured to apply a fluid stream that vibrates at amegasonic frequency onto the bottom surface of the substrate therebycausing the substrate to vibrate mechanically at the megasonicfrequency; and a second nozzle, located at a second side of thesubstrate, configured to discharge a chemical solution onto the topsurface of the substrate.

The present disclosure provides a method of cleaning a substrate inaccordance with various embodiments. The method includes directing anacoustically agitated fluid stream at a first surface of a substrate tocause the substrate to vibrate mechanically at a megasonic frequencythereby dislodging contaminant particles on the first surface of thesubstrate, wherein the first surface of the substrate is opposite asecond surface of the substrate, wherein the second surface of thesubstrate includes a pattern.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A system for cleaning a photomask, comprising: abracket that is configured to support the photomask and is located at afirst side of the photomask; an acoustic energy generator configured togenerate acoustic energy, wherein the acoustic energy includesmechanical vibrations of a megasonic frequency and wavelength; and afluid dispenser coupled to the acoustic energy generator such that theacoustic energy generated by the acoustic energy generator is receivedby the fluid dispenser to generate an acoustically agitated fluid streamdirected at a second side of the photomask, wherein the first side ofthe photomask is opposite a second side of the photomask, and whereinthe first side includes a pattern.
 2. The system of claim 1, wherein thebracket is configured to move the supported photomask horizontally in arotational motion.
 3. The system of claim 2, wherein the bracket isconfigured to rotate the supported photomask at a rotation speed rangingfrom 0 to 500 radius per minute (rpm).
 4. The system of claim 1, whereinthe acoustically agitated fluid stream is composed of cleaning fluidthat includes at least one of: ozone water, teramethylammonium hydroxide(TMAH), carbon dioxide (CO₂) dissolved in water, hydrogen (H₂) dissolvedin water, and standard clean 1 (SC1).
 5. The system of claim 1, whereinthe megasonic frequency ranges between 1 and 3 megahertz (MHz).
 6. Thesystem of claim 1, wherein the photomask is an extreme ultraviolet (EUV)photolithography mask.
 7. The system of claim 1, wherein theacoustically agitated fluid stream is directed at the second side of thephotomask at an angle between about 60 degrees to about 90 degrees.
 8. Asystem of cleaning a substrate, comprising: a bracket that is configuredto support and horizontally rotate a substrate having a top surface andan opposing bottom surface, wherein the top surface includes a pattern;a first nozzle, located adjacent the bottom surface of the substrate,configured to apply a fluid stream that vibrates at a megasonicfrequency onto the bottom surface of the substrate thereby causing thesubstrate to vibrate mechanically at the megasonic frequency; and asecond nozzle, located at a second side of the substrate, configured todischarge a chemical solution onto the top surface of the substrate. 9.The system of claim 8, wherein the first nozzle and the second nozzle isrespectively to apply the fluid stream that vibrates at the megasonicfrequency onto the bottom surface of the substrate and discharge thechemical solution onto the top surface of the substrate at the sametime.
 10. The system of claim 8, wherein the substrate is an extremeultraviolet photomask.
 11. The system of claim 8, wherein the fluidstream is composed of cleaning fluid that includes at least one of:ozone water, teramethylammonium hydroxide (TMAH), carbon dioxide (CO₂)dissolved in water, hydrogen (H₂) dissolved in water, and standard clean1 (SC1).
 12. The system of claim 8, wherein the bracket is configured torotate the substrate at a rotation speed ranging from 0 to 500 radiusper minute (rpm).
 13. The system of claim 8, wherein the megasonicfrequency ranges between about 1 megahertz (MHz) to about 3 MHz.
 14. Thesystem of claim 8, wherein the first nozzle is placed beneath thesubstrate with an angle that is between about 60 degrees to about 90degrees.
 15. The system of claim 8, wherein the vibration of the fluidpath is generated by an acoustic energy generator that is coupled to thefirst nozzle.
 16. A method, comprising: directing an acousticallyagitated fluid stream at a first surface of a substrate to cause thesubstrate to vibrate mechanically at a megasonic frequency therebydislodging contaminant particles on the first surface of the substrate,wherein the first surface of the substrate is opposite a second surfaceof the substrate, wherein the second surface of the substrate includes apattern.
 17. The method of claim 16, wherein the acoustically agitatedfluid stream is composed of cleaning fluid that includes at least oneof: ozone water, teramethylammonium hydroxide (TMAH), carbon dioxide(CO₂) dissolved in water, hydrogen (H₂) dissolved in water, and standardclean 1 (SC1).
 18. The method of claim 16, further comprising whiledirecting the acoustically agitated fluid stream at the first surface ofthe substrate, simultaneously apply a chemical solution onto the secondsurface of the substrate, the second chemical being different than theacoustically agitated fluid stream.
 19. The method of claim 16, whereinthe substrate is an extreme ultraviolet (EUV) photolithography mask. 20.The method of claim 16, wherein directing the acoustically agitatedfluid stream at the first surface of the substrate includes directingthe acoustically agitated fluid stream at an angle between about 60degrees and about 90 degrees relative to the first surface of thesubstrate.